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 At 55% rpm. the ECB de-energises the starter motor, turns off the exciter and de-energises the gearbox de-oiling valve. 5 sec. after speed has reached 55% rpm. the backup start contactor is de-energised. The start in progress signal is de-activated, steady state speed control is initiated and run state is entered. When the engine has reached 95% rpm. the surge control system is initiated. 2 sec. later the ECB sends an 'AVAILABLE' signal to the aircraft circuits. The AVAIL legend in the APU START pushbutton switch 2KA comes on. It indicates that the APU is ready to supply bleed air and electrical power to the aircraft systems.
 When the APU BLEED pushbutton switch 5HV is set to the ON position, the bleed contol valve will open. The APU will then supply bleed air to the pneumaticsystem. The ECB controls the bleed control valve, which supplies the pneumatic system with bleed air and protects the load compressor from surge. The EGT increases when a selection of pneumatic or electrical load, or both, is made. This is shown on the lower ECAM display unit of the Electronic Centralized Aircraft Monitoring (ECAM). During the start sequence the IGVs are fully closed. With the engine speed at 95% rpm, +2 sec. the ECB will accept pneumatic and electrical demand signals. It computes the position of the IGVs and supplies the necessary pneumatic flow. The pneumatic and electrical loads together can cause the EGT to increase more than the set temperature limit. If this occurs, the ECB commands the IGVs to move nearer to the closed position from the set position. This reduces the pneumatic load and makes the electrical load the primary load.

 When the MASTER SW 14KD is set to the OFF position, a normal APU shutdown starts. The ECB causes the IGVs to move to the closed position and the bleed control valve to the discharge position. The ECB then removes the 'AVAIL' signal to the aircraft circuits.With the pneumatic loads removed and the bleed air supply no longer required, the APU goes into a cool-down cycle for 120 sec. The AVAIL legend in the APU START pushbutton switch 2KA and AVAIL indications on the upper and lower ECAM displays are then turned off. A decrease in the EGT shows on the APU page of the ECAM. After the cool-downcycle ends, APU speed drops below 95%. The ECB then takes a condition monotoring snapshot and starts the shutdown. The ECB then turns off the fuel valve and fuel servo and turns on the gearbox de-oiling valve. During the run-down cycle, when the engine speed is below 7% rpm, the ECB closes the air intake flap. Before it de-energizes itself, the ECB updates the nonvolatile memory and signals the aircraft circuits to:
 -stop the fuel feed pump 4QC,
 -close the FUEL LP VALVE 3QF.
 The ECB continually monitors the APU operation and protection functions. If necessary, it shuts down the APU or gives a visual indication to the operator. When a malfunction occurs that could cause damage to the engine, the ECB automatically unloads the engine and starts a shutdown. The FAULT legend in the MASTER SW 14KD comes on. It will stay on until the MASTER SW 14KD is released to OFF.
 4. Operational Characteristics___________________________
 A. Operating Limits
 (1)
 Rated combination load at sea level 38 DEG.C (100 DEG.F) condition: Bleed Load: Bleed flow = 1.07 Kg/s (142 lbs/min),

 Bleed pressure = 3.33 bar 48.95 psi), Shaft load: 83KW (111.3 shp).

 (2)
 Maximum EGT limits (which result in a shutdown):

 -
max. EGT at 100% speed ...............=> 682 deg.C (1259.6 deg.F);

 -
max. EGT during start (below 25000ft) => 900 deg.C (1652 deg.F);

 -
max. EGT during start (above 25000ft) => 982 deg.F (1799.6 deg.F).

 

 (3)
 Generator output shaft speed: - 24034 rpm.

 

 B. Fuel and Fuel Control System
 NOTE : This is for general reference only. All fuel types approved in
____ your Flight Crew Operation Manual (FCOM) can be used in the APU.
 (1)
 The fuel inlet minimum pressure is 0.7 bar (10 psi) maximum is 3.8 bar (55.0 psi). 5 psi above true vapour pressure is limited to less than 30 sec.

 (2)
 Fuel inlet temperature from - 40 DEG.C (-40 DEG.F) to 54 DEG.C. (130

 DEG.F). ------------------------------------------FUEL SPECIFICATIONS ------------------------------------------
JET A /JET A1  ASTM D 1655
 JP 4  MIL T 5624
 JET B  ASTM D 1655
 JP 5  MIL T 5624
 JP 8  MIL T 5624
 RT  GOST 10227
 TS-1  GOST 10227
 (3) Oil and Fuel Leakage limits

 (a) Oil and Fuel leakages are not permitted.
 C. Engine Starter Motor-Duty Cycle Three consecutive start attempts are permitted without cooldown. After the third start attempt the starter must cool down for at least 60 minutes.
　
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